Short answer: I wasn't sure I was going to stick with SPD-SL when I first tried them, but for the type of riding I do, I ended up sticking with them. On the bike where I am more likely to do a lot of walking around, I still have SPD. On the bike where I don't, I stuck with SL.

I went to SPD-SL on my road bike years ago, still use SPD on my beater/hybrid bike (and in spin classes over the winter.) I actually put two sided pedals on that one - rides with my wife or rides with more walking than riding, I don't use cleats at all.

I definitely prefer the feel of the SPD-SL pedals - more locked in and just feels like more power going to the pedal. On the road bike I'm typical doing longer rides/longer times between stops/not much walking around.

Walking around definitely sucks in the SPD-SLs but unless you are really walking around in crazy stuff, the part that actually clips in on the SPD-SL pedal rarely gets clogged up for me. I bought some cleat covers that I keep in my saddle bag, easy enough to snap them on.

On tours that involve overnight stays, or one way trips I do several times per year where I will change clothes when I arrive, I have to carry sandals or sneakers, where with the SPD shoes I can get by just wearing them when off the bike. But, for those long rides still not much walking around and on long rides I still like the feel of the SLs better.

The SPD-SL cleats also require more care in setting up - there is another degree of freedom compared to the just one direction with the two hole cleats. For me, the SL plastic cleats wear out faster than the metal SPD cleats and cost about the same, if not more - SL is more expensive.

So, the usual YMMV answer! If I only had one bike, had to choose one or the other, and all I did was the typical road riding I do, I'd probably only have SL. If I only had one bike and most of my riding involved more walking or more overnight touring, I'd probably choose SPD.